The bulk fluorescein diacetate assay (FDA) as a technique for evaluating biotic impacts of crude oil to coastal sediments

This study adapted the bulk fluorescein diacetate (FDA) assay to evaluate the impact of crude oil on biological activity levels in marine sediments. Sediment cores from the Elkhorn Slough, California were incubated with different levels of sweet crude oil (Deepwater Horizon, Macondo Prospect) in the Moss landing Marine Laboratories aquarium facility over a 30-day period. During this period, the amount of fluorescein released, concentration of oxygen in overlying waters, and flux of oxygen into the sediments were monitored. For all treatments a strong negative correlation between added oil and FDA production was observed (p < 0.05). The concentration of oxygen in the first 2 mm of sediment cores decreased linearly with the addition of crude oil and correlated positively with fluorescein released (p < 0.05). A linear increase in sediment oxygen flux was also observed upon crude oil addition. The miniaturized bulk FDA assay could be powerful in evaluating oil spill impacts in coastal systems.